Generic name: Diphenhydramine hydrochloride.

Other brand names: AllerMax, Banophen, Belix, Diphen Cough, Dormarex-2, Genahist, Hvdramine, Nervine Nighttime, Nidryl, Nordryl, Nytol, Phendry, Sleep-Eze 3, Sominex, Twilite.

Benadryl is an antihistamine. Antihistamines block the effects of histamine, a body chemical that causes swelling and itching. 

Quick Facts About Benadryl


Used to treat symptoms of allergy – red, inflamed eyes; itching, swelling and redness from hives and other rashes caused by allergies. Also used to relieve symptoms of seasonal allergies – sneezing, coughing, runny or stuffy nose. Is also used to treat allergic reactions to blood transfusions, to prevent and treat motion sickness, to prevent severe allergic reaction, and to treat Parkinson’s disease.

Benadryl Dosage

Take exactly as prescribed.

  • Usual adult dose: 25 to 50 milligrams 3 or 4 times per day. As a sleep aid — 50 milligrams at bedtime. For motion sickness — first dose 30 minutes before motion, other doses before meals and at bedtime, as long as motion continues.
  • Usual child dose(20 pounds and over): 12.5 to 25 milligrams 3 to 4 times per day, not to exceed 300 milligrams per day. Do not use as a sleep aid for children under age 12.
  • Missed dose: take as soon as possible, unless almost time for next dose. In that case, do not take missed dose, go back to regular schedule. Do not double doses.

Benadryl Side Effects

Overdose symptoms:

central nervous system depression or stimulation, especially in children; dry mouth; fixed, dilated pupils; flushing; stomach and intestinal symptoms. If you suspect an overdose, immediately seek medical attention.

More common side effects: disturbed coordination, dizziness, excessive calm, increased chest congestion, sleepiness, stomach upset.

Less common Benadryl side effects: anaphylactic shock (extreme allergic reaction), anemia, blurred vision, chills, confusion, constipation, convulsions, diarrhea, difficulty sleeping, double vision, dry mouth, dry nose, dry throat, early menstruation, excessive perspiration, excitation, fast or fluttery heartbeat, fatigue, frequent or difficult urination, headache, hives, inability to urinate, increased sensitivity to light, irregular heartbeat, irritability, loss of appetite, low blood pressure, nausea, nervousness, rapid heartbeat, rash, restlessness, ringing in the ears, stuffy nose, tightness of chest and wheezing, tingling or pins and needles, tremor, unreal or exaggerated sense of well-being, vertigo, vomiting.


Inform your doctor before combining Benadryl with:

antidepressant drugs known as MAO inhibitors such as Parnate and Nardil; sedative/hypnotics such as Halcion, Nembutal, and Seconal; tranquilizers such as Xanax and Valium.

Alcohol may increase sedative effects; do not drink alcohol when taking this medication.

Special Cautions

If pregnant or planning to become pregnant, inform your doctor immediately. Not advised for use when nursing an infant.

May cause dizziness, excessive calm, or low blood pressure.

Follow doctor’s instructions carefully for children, can cause excitability.

  • Do not take if sensitivity to or allergic to this or other antihistamines.
  • May cause drowsiness and impair your ability to drive a car or operate machinery. Do not take part in any activity that requires alertness.
  • Use carefully if you have: difficulty urinating due to bladder obstruction, heart disease, high blood pressure, history of asthma or other chronic lung disease, intestinal blockage, narrow-angle glaucoma, narrowing of the stomach or intestine due to stomach problems, over-active thyroid, or symptoms of enlarged prostate.

Note: provides accurate and independent information prescription pills, over-the-counter medicines and natural products. This material is provided for educational purposes only and is not intended for medical advice, diagnosis or treatment. If you have questions about  dosage, or Benadryl side effects, please contact your healthcare provider.